1. Field of the Invention
The present invention relates to a cooling system of ring segment that is applied to a gas turbine, and to a gas turbine.
2. Description of Related Art
Conventionally, since combustion gas of a high temperature and high pressure passes through the turbine section of a gas turbine, which is used in the generation of electrical energy, cooling of the ring segment and the like is important in order to continue stabilized operation. In particular, due to improvements in the thermal efficiency of gas turbines in recent years, the temperature of combustion gas continues to increase, and so further enhancement of the cooling performance is required.
FIG. 10 shows a block diagram of a conventional gas turbine. In it a gas turbine 1 is constituted by a compressor 2 that compresses air for combustion, a combustor 3 that injects fuel FL into the compressed air that is sent from the compressor 2, causes a combustion, and generates combustion gas, a turbine section 4 that is positioned on the downstream of this combustor 3 in the flow direction of the combustion gas and driven by the combustion gas that has left the combustor 3, a generator 6, and a rotating shaft 5 that integrally connects the compressor 2, the turbine section 4, and the generator 6.
FIG. 11 is a cross-sectional view that shows the internal structure relating to the turbine section 4 of the gas turbine.
The gas turbine supplies combustion gas FG generated in the combustor 3 to a turbine vane 7 and a turbine blade 8, and by causing the turbine blades 8 to rotate around the rotating shaft 5, converts rotational energy into electrical power. The turbine vanes 7 and the turbine blades 8 are alternately disposed from the upstream to the downstream in the flow direction of the combustion gas (in the direction from the left side to the right side on the sheet of FIG. 11). Moreover, a plurality of turbine blades 8 is disposed in the circumferential direction of the rotating shaft 5, and thus rotates together with the rotating shaft 5.
FIG. 12 is an essential portion cross-sectional view of a conventional ring segment. The ring segment 60 is formed from a plurality of segment bodies 61 that is disposed in an annular shape in the circumferential direction of the rotating shaft 5, and as a whole forms a circular shape centered on the rotating shaft 5. Each segment body 61 is supported by a casing 67 via hooks 62 and a isolation ring 66. Moreover, a collision plate 64 that is supported from the isolation ring 66 is provided with a plurality of small holes 65, and cooling air CA that is supplied to the casing 67 blows out to below from the small holes 65, and carries out impingement cooling of the upper surface of the main body of the segment body 61. Also, in the segment body 61, a plurality of cooling passages 63 is disposed in the axial direction of the rotating shaft 5, and the cooling air flows in the axial direction inside the main body of the segment body 61, and performs convection cooling of the segment body 61. Also, the ring segment 60 is disposed annularly on the outer periphery side of the turbine blades 8 centered on the rotating shaft 5, and between the ring segment 60 and the tip of the turbine blades 8, a certain tip clearance is provided in order to avoid mutual interference. Note that a downstream end face 69 of the segment body 61 on the downstream in the flow direction of the combustion gas is positioned further on the downstream in the flow direction of the combustion gas than the trailing edge TE of the rotating turbine blades 8.
FIG. 13 is a perspective view of the ring segment 60 shown in FIG. 12. In this example, openings 33 are arrayed in the side end portion 70 of the segment body 61 along the axial direction of the rotating shaft 5 (in the direction from the lower left side to the upper right side on the sheet of FIG. 13). When cooling air after impingement cooling of the main body of the segment body 61 is supplied to a cooling passage (not illustrated) that is provided in the side end portion 70, and blown out from the openings 33 into the combustion gas, it performs convection cooling of the side end portion 70.
In order to cool the ring segment 60, cooling air that is a portion of the extracted air of the compressor 2 is supplied from the supply hole of the casing 67 to each segment body 61 of the ring segment 60. The cooling air is blown into a cooling space 71 that is enclosed by the collision plate 64 and the segment body 61 via the small holes 65 that are opened in the collision plate 64, and performs impingement cooling of the upper surface of the main body of the segment body 61 (the surface in contact with the cooling space). The cooling air after the impingement cooling is blown from the downstream end face of the segment body 61 in the flow direction of the combustion gas via the cooling passage 63 into the combustion gas, and the main body of the segment body 61 is convection cooled by the cooling air. Also, by discharging a portion of the cooling air from the openings 33 that are disposed along the side end portion 70 into the combustion gas, the side end portion 70 of the segment body 61 is convection cooled.
Patent Document 1 discloses one example of the aforementioned cooling system of ring segment.